1. Field of the Invention
This invention relates to computer databases, and in particular to a method of selecting and representing time-varying data from a time-relational database management system.
2. Description of Related Art
A database management system (or "DBMS") is generally a complex computer program designed to define data records, add, delete, and modify such records, and output selected parts of such records to a computer display screen or printed reports. Records are collections of related data typically organized in fields each having pre-defined characteristics. Records of a similar type are stored in one or more files.
In some applications, a DBMS may be adapted to generate and retain records that change over time but which relate to a single DBMS entity (such as a customer or product). Such DBMS maintain a file of "master" records containing current information. Such a DBMS also typically maintains a file of one or more "history" records for each master record, indicating pre-change versions of the master record, and a file of "future" or "pending" records associated with a master record, indicating changes that are to be made to the master record at a specified time or upon the occurrence of a specified event. Such DBMS' are known as time-relational database management systems (or "TDBMS").
A TDBMS may also maintain a file of error records, showing changes that have not been applied to a corresponding master record or entered into the pending record file due to internal errors (such as out-of-range data or mis-typed data).
An important function of a well-designed DBMS is the ability to output information in a concise but understandable manner. Most DBMS' have a "browse" function that permits a user to display a "view" of selected data relating to an entity on a computer display screen, and to access the corresponding data for a next or a previous entity at the touch of a key. A "view" may comprise some or all of the data fields of a logical record (which itself comprises one or more physical records), or some or all of the data fields of multiple logical records.
The function of browsing may be useful to view records belonging to different entities, such as customers or products, where the data fields are expected to change significantly between records. However, for a particular entity, such as a single customer, simple browsing between the time-related records (i.e., pending and history records for that entity) can be confusing and lead to errors, since small differences between the data fields from one time-related record to a next may not be obvious to the user.
The present invention provides a solution to the problem of viewing time-related data records such that differences in the master, pending, and history records for a particular entity are clearly evident to a user. The present invention also provides a method for clearly indicating to a user differences between a master or pending records and any error records.